The present invention relates to a display apparatus that makes it possible to view an image with parallax information, a plate-shaped filter attached to such a display apparatus, a filter position adjusting mechanism, and a filter position adjusting method, and particularly to a filter position adjusting mechanism and a filter position adjusting method for mounting a divided wave plate filter with high precision for display of an optimum stereoscopic image.
Conventionally, various attempts have been made for technology of representing a three-dimensional image, and methods of display of a three-dimensional image have been studied and put to practical use in many fields such as photography, movies, television and the like. Methods of displaying a three-dimensional image are roughly classified into methods of a glasses type and methods of a no-glasses type. Both types of methods input an image with binocular parallax to a right and a left eye of an observer, so that the image can be viewed as a stereoscopic image. Typical glasses type methods include anaglyph methods in which so-called red and blue glasses are worn and polarizing glasses methods. Color separation methods such as the anaglyph methods have many disadvantages in terms of quality, such as difficulty in color representation, degradation in a field of view and the like. The polarizing glasses methods in general had problems such as necessity of using two projectors However, a method of enabling stereoscopic display with a single direct view type display apparatus has recently been proposed.
FIG. 1 schematically shows a stereoscopic image display apparatus using the polarizing glasses method. A stereoscopic image display apparatus 200 has a structure formed by a liquid crystal panel unit 201 and a divided wave plate filter unit 202 attached to the liquid crystal panel unit 201. The liquid crystal panel unit 201 has a pair of transparent supporting substrates 204 and 206 formed between a pair of polarizing plates 203 and 207, and a pixel liquid crystal unit 205 having RGB pixels formed therein which unit is disposed between the pair of transparent supporting substrates 204 and 206. A divided wave plate filter unit 202 is disposed on a surface of the liquid crystal panel unit 201. The divided wave plate filter unit 202 has a structure in which a divided wave plate 208 is disposed in every other line on one side of a transparent protective substrate 209, for example. The divided wave plate filter unit 202 is also referred to as a μ-Pol or micropolarizer.
The stereoscopic image display apparatus 200 of such a structure rotates a direction of linearly polarized light emitted from the liquid crystal panel unit 201, and thereby converts pieces of the linearly polarized light from an even-numbered line and an odd-numbered line of the display screen into pieces of linearly polarized light perpendicular to each other. That is, the linearly polarized light from the liquid crystal panel is emitted as it is from the even-numbered line, and in the odd-numbered line, the divided wave plate 208 acts to convert the linearly polarized light from the liquid crystal panel into linearly polarized light perpendicular to the linearly polarized light from the liquid crystal panel. When the light of the display apparatus is observed by glasses 210 having polarizing directions perpendicular to each other, light of an image for a right eye enters the right eye, and light of an image for a left eye enters the left eye. By looking through the glasses 210, it is possible to observe a full-color, flicker-free stereoscopic image.
In addition, a stereoscopic image display apparatus of the no-glasses type has been devised which uses a wave plate filter as described above effectively to eliminate the need for an observer to wear the glasses (see Japanese Patent Laid-Open No. Hei 10-63199). Furthermore, as an example that uses a wave plate filter as described above effectively, a system that displays two or more mixed pictures on a single display screen potentially having an image separating mechanism and extracts predetermined original images by the image separating mechanism has been devised by the present inventor et al., such as a double-screen display for displaying multiple screens from a single display screen (see Japanese Patent Laid-Open No. Hei 11-249593).
However, when the divided wave plate filter unit 202 is mounted on the display apparatus having the liquid crystal panel unit 201 and the like, the divided wave plate filter unit 202 needs to be securely fixed to a mounting position corresponding to a predetermined region (pixel position) of the display apparatus. This is not easy, and causes the following problems.
A first problem occurs in mounting the divided wave plate filter unit. Since the foregoing display method divides the display screen into predetermined regions and thus uses the display screen, it is effective to make the divided regions as fine as possible in a nested manner for enhanced resolution. While a high-definition panel is available as pixels on a display screen with an increasingly high resolution have become finer, it is extremely difficult to fabricate the corresponding high-definition wave plate filter and fix the divided wave plate filter unit fabricated by the different process with high precision in correspondence with pixels corresponding to the predetermined regions.
Even if the divided wave plate filter unit can be mounted with high precision, the divided wave plate filter unit is generally fixed by a resin or the like, and therefore positional displacement tends to occur during a fixing period before the resin is cured even after the position of the divided wave plate filter unit is adjusted once. In addition, various factors such as vibration during transportation, heat and the like often cause positional displacement. A glass substrate is generally used for the divided wave plate filter unit to maintain precision of the predetermined regions in many cases because of problems in manufacturing, and hence its own weight, in particular, causes positional displacement. In addition, positional displacement of the filter may be caused due to various conditions in durability such as deterioration of the fixing agent and the like. Once the cured resin is displaced, it is extremely difficult to thereafter correct the position, and thus the relatively expensive display panel will be totally wasted.
Furthermore, the stereoscopic image display system has a characteristic in that an optimum disposing position of the filter is determined by a height position of an eye of an observer at the time of viewing. This presents a problem in that a prefixed position is not necessarily the optimum position at the time of observation. FIG. 2 shows such a state. A display apparatus 220 in FIG. 2 is formed by a pixel unit 223 sandwiched between transparent supporting substrates 221 and 222 and a divided wave plate filter unit 225. In the figure, the optimum disposing position of the wave plate filter for an observer at an observation position α is a position of the wave plate filter indicated by solid lines, and similarly the optimum disposing position of the wave plate filter for an observer at an observation position β is a position of the wave plate filter indicated by broken lines in the figure. Thus, as is clear from FIG. 2, the optimum disposing position of the filter is determined by the height position of an eye of an observer at the time of viewing, or even by an angle of the liquid crystal panel and monitor and the like. Hence, this presents a problem in that a position at which the divided wave plate filter unit is prefixed is not necessarily the optimum position at the time of observation of the divided wave plate filter unit.
Further, the factors as described above cause a problem in that displacement of the divided wave plate filter unit by a few to a few ten % of a pixel (a few ten μm in the above example) is observed as a significant cross talk between images. When the divided wave plate filter unit is mounted properly, light from corresponding pixels passes through a corresponding wave plate region at all times, and light from pixels other than the corresponding pixels does not pass through the corresponding wave plate region. However, in a case where the divided wave plate filter unit slants, even when the displacement is only about a few to a few ten % of a pixel, or an absolute amount of displacement is about 50 μm, for example, an amount of displacement in a vertical direction at both edges becomes large, and therefore some of the light from the corresponding pixels may not pass through the corresponding wave plate region. This results in a problem in that cross talk between images occurs and hence a good stereoscopic image cannot be displayed.
Conventionally, in mounting the divided wave plate filter unit, a synthetic image for stereoscopic display similar to an ordinary image is displayed on a screen, and then the position of the divided wave plate filter is determined on the basis of whether the image can be actually viewed as a stereoscopic image with polarizing glasses worn. However, whether the image can be viewed as a stereoscopic image is determined very vaguely; it is therefore desired to be able to position the divided wave plate filter by using a more exact method.